1. Field of the Invention
The present invention relates to a straddle-type vehicle.
2. Technical Background
There is a possibility that a relatively heavy load is applied to a vehicle body in a straddle-type vehicle, such as an off-road vehicle capable of driving on an irregular terrain. Therefore, relatively high rigidity for the vehicle is demanded.
As a method for improving the rigidity of the vehicle, use of a body frame with relatively high rigidity has been considered. For example, a so-called cradle-type body frame disclosed in JP-A-2001-278158 can be implemented as a body frame with relatively high rigidity. More specifically, the cradle-type frame generally includes a head pipe, a main frame, a down frame, a lower frame, and a seat rail. The main frame extends downward to the rear from the head pipe. The down frame extends downward to the rear from the head pipe in a position below the main frame. An end of the main frame and an end of the down frame are connected to each other through the lower frame. Accordingly, a loop-shaped space in a plan view is formed with the main frame, the down frame, and the lower frame. An engine is mounted in this loop-shaped space in a plan view in the straddle-type vehicle employing the cradle-type body frame.
As described above, frames are placed above and below the engine in the cradle-type body frame. Therefore, it is commonly known that relatively high rigidity can easily be obtained with the cradle-type body frame. However, depending on a type of a straddle-type vehicle and intended use thereof, there is a need for further improvement in the rigidity of the body frame.
For example, metal members constituting the body frame can be thickened in order to further improve the rigidity of the body frame. However, thickening of the metal members constituting the body frame tends to cause an increase in the body frame weight. Thus, when it is attempted to improve the rigidity of the vehicle merely by improving the rigidity of the body frame, the vehicle weight tends to be increased.